With 80 ohms, the DT 770 PRO differs significantly from the 32- and 250-ohm versions in terms of sound.
The 80-ohm version of the DT 770 PRO has a two-part coil system and reacts somewhat more slowly, which causes a slight treble attenuation at approx. 6 kHz. This can be very pleasant for ears that are sensitive to high frequencies. The DT 770 PRO versions with 32 and 250 ohms have a three-part coil system. This ensures a faster performance and reproduces the high frequencies more faithfully, which is why the treble sounds more present.
The 32 and 250 ohm versions have the same sound signature, but differ in the ear cushions. The DT 770 PRO in 32 ohms has ear cushions made of synthetic leather, which slightly amplify the bass and attenuate the treble in the presence range. The DT 770 PRO in 250 ohms (velour ear cushions) has a slightly finer resolution, which can only be perceived with a very fine ear.
If you have a low-power sound card, e.g. the internal sound card of a laptop or your smartphone, then you should opt for the DT 770 PRO with 32 ohms, as this produces the highest volume. Users with very powerful sound cards or amplifiers can select a higher impedance if required.
The 80-ohm DT 990 PRO also has a two-part coil system and reacts somewhat more slowly, which is why a slight treble attenuation can also be detected here at approx. 6 kHz. This makes the sound somewhat softer in the treble. The 250-ohm version has a three-part coil system for slightly faster performance. As a result, the high frequencies are also reproduced more faithfully with this model, while the treble sounds more present.